Apparatus for detecting breakage of blade of rotary cutter

ABSTRACT

An apparatus is provided for detecting breakage of at least one of blades of a rotary cutter for a tow. The apparatus comprises a first detector which produces a pulse for every pass of a tip of the cutter blade across a predetermined position, a second detector which produces a pulse or the definite number of pulses for every rotation or every definite number of rotations of the rotary cutter, and a discriminator receiving the output pulses from the both detectors to produce an abnormal signal when the number of pulses produced by the first detector during a period of time of the pulses produced by the second detector is smaller than a predetermined value.

United States Patent [191 Fujimaki et al.

[ 1 APPARATUS FOR DETECTING BREAKAGE OF BLADE 0F ROTARY CUTTER [75] inventors: Masaru Fujimaki; Takehiko Okamoto; Mikio Tashiro, all of Matsushima, Japan [73] Assignee: Teijin Limited, Osaka, Japan [22] Filed: Feb. 14, 1973 [21] Appl. No.: 332,380

[30] Foreign Application Priority Data 7 Mar. 3, 1972 Japan 47-22050 [52] US. Cl. 235/92 PD, 235/92 V, 235/92 R, 83/621 [51] Int. Cl. G06m 3/02 [58] Field of Search...- 235/92 PD, 92 PE, 92 V, 235/92 EC, 92 PB; 83/62,.522, 62.1

[56] References Cited UNITED STATES PATENTS 3.019.346 1/1962 La ycak 235/92 V 1 Oct. 22, 1974 3,234,360 2/1966 Schooley 235/92 PE 3,652,987 3/1972 McCarthy 235/92 EC 3,659,081

4/1972 Piccione 235/92 PE Prir'nary Examiner-Paul .l. Henon Assistant Examiner-Joseph M..Thesz, Jr. Attorney, Agent, or Firm-Wenderoth, Lind & Po'nack ABSTRACT An apparatus is provided for detecting breakage of at leastone of blades of a rotary cutter for a tow. The apparatus comprises a first detector which produces a pulse for every pass of a tip of the cutter blade across a predetermined position, a second detector which produces a pulse or the definite number of pulses for every rotation or every definite number of. rotations of the rotary cutter, and a discriminator receiving the output pulses from the both detectors to produce an abnormal signal when the number of pulses produced by the first detector during a period of time of the pulses produced by the second detector is smaller than a predetermined value.

-14 Claims, 18 Drawing Figures PATENTEDnmzz new SHEEI 1 0F 7 SCHMITT I 05C. m CIRCUIT 13 REASONANCE CIRCUIT mamznumz 1914 3343311 am am 1 Fl 6 .5 13 DIFFERENTIAL 105 S 106 CIRCUIT S 1QUT P8 102 103 5211 R O [H4 107 03 1 11- Q Q3 L RESET mamanome mm 31843371 SHEEI 7 If 7 MONOSTABLE MULTIVIBRATOR DIFFERENTIAL F I G 9 (a CIRCUIT 1 3 P5151 15,2 15 E i 5&

APPARATUS FOR- DETECTING BREAKAGE OF BLADE OF ROTARY CUTTER This invention relates to an apparatus for detecting breakage of at least one of blades of a rotary cutter for a tow.

Widely known typical apparatus for cutting a tow or the like to a predetermined length comprises a pair of shallow tub-shaped cylindrical disks and a rotating cutter having a plurality of radially extending blades. Each disk has slots along a cylindrical flange thereof. The slots of the two disks are so disposed as to come into alignment with each other successively as the two disks rotate in. the opposite directions, and the tow to be cut is fed between the flanges of the two disks. The cutter blades pass through the aligned slots to cut the tow to a predetermined length.

The cutter blade usually develops very small or fine cracks at the base of the blade due to distortion caused while the blade material is being processed, grinding of the blade. or impact at the time of cutting the tow. Furthermore, wear due to stress will be accumulated during the time of cutting the tow and the blade tends to be brokenat the base of the blade in which cracks developed.

Breakage of the cutting blade while the rotary cutter is in operation does not at all affect the operation itself. Hence the operators often do not find the occurrence of such breakage of the blade and continue the operation. As a result. if it is assumedthat only one blade is broken, the tow across which the blade 2 By specifying the interrelationships among such first detector, second detector, and the discriminator, the present invention may be embodied as follows:

First. the second detector produces n units of pulses for every rotation of the rotary cutter, the pulses being produced to have a period of time during which one pulse is produced by said first detector. The discriminator receives the output pulsesfrom both detectors to produce an abnormal signal when no pulse is received would have passed remains uncut, resulting in, say,

double-length cut" abnormal products having twice the predetermined length. Such double-length cut abnormal products often cause trouble in spinning or in other processings.

Accordingly, an object of this invention is to provide an apparatus for detecting breakage of the blade of a rotary cutter at an early time.

Another object of this invention is to provide a detecting apparatus which does not require adjustment even if the cutting speed is varied.

Still another object of this invention is to provide a detecting apparatus which allows for easy adjustment when the number of cutter blades is changed.

A further object of this invention is to minimize the production of double-length cut abnormal products,v

thereby omitting regular checking work by operators.

To achieve the above-mentioned objects, the present invention provides an apparatus for detecting breakage of at least one of the blades of a rotary cutter for a tow in which n (an integer of 2 or more) blades are radially disposed, comprising: a first detector which produces a pulse for every pass of-a tip of the cutter blade across a predetermined position; a second detector which produces a pulse or a definite number of pulses for every rotation or every definite number of rotations of said rotary cutter, said pulses being produced to have a period of time during which the number of pulses pro-' duced by said first detector normally reaches a predetermined'value; and a discriminator receiving the output pulses from said both detectors to produce an abnormal signal when the number of pulses produced by the first detector during said period of time defined by from the first detector during the pulse period of the second detector.

Second, the second detector produces one pulse for every rotation of the rotary cutter, the pulses being produced in a period of time during which n units of pulses are produced by the first detector. The discriminator receives the output pulses from the both detector to produce an abnormal signal when the number of pulses produced by the first detector during the period of time defined by pulses produced by the second detector is smaller than n units.

. Third, the second detector produces one pulse for every m (an integer of 2 or more) revolutions of the rotary cutter, the pulse being'produced to have a period of time during which n m unitsof pulses are produced by the first detector. The discriminator receives the output pulses from bothdetectors to produce an abnormal signal when the number of pulses produced by the first detector over a period of time determined by pulses; produced by the second detector is smaller than reference value determined at near the n m and (n-l )m. g v A .dstsstins me n tel u in th abov mentioned first and second dete ctors, a known photo electric switch or an proximity switch which is magnetically actuated when a ferromagnetic metal piece approaches may be used.

The above and further novel features and objects of this invention will appear more fully from the following detailed description when the same is read in connection with the accompanying drawings, and the novel features will be particularly pointed out in the appended claims.

In the figures where like elements are referenced alike: FIG. 1 is a perspective view showing major portions of an apparatus for detecting broken blades of a rotary cutter.

' FIG. 2 is a in FIG. 1. FIG. 3is a circuit diagram of the second detector shown in FIG. 1. g t

FIG. 4a to FIG. 9a are circuit diagrams of different discriminators which receive output signals from the first and second detectors. y

FIG. 4b to FIG.9b and FIG, 7c are time charts of the circuit diagrams of FIG. 4a'to FIG. 9b. u

FIG. 10 shows a switch circuit which is operated by the abnormal signals from theabove-mentioned discriminators, and Y FIG. 11 is a perspective view showing another emcircuit diagram of the first detector shown bodiment of the first detector and the second detector.

said pulses produced by said second detector is smaller than a predetermined value.

spaced from each other along the curved cylindrical center between I flanges 3 and 4 of said disks, said slots being parallel to the shafts 7 and 8 upon which the disks are mounted. One end of each of the slots opens out of the side edge of the flange 3 and 4. These disks are so disposed that when the open sides face in thesame direction and the curved flange surfaces are adjacent each other, corresponding slots and 6 are in alignment with each other. The disks 1 and 2 are of the same size and they rotate at the same speed in the directions of arrows C and D respectively. A tow A that is delivered from the direction of arrow B is held between the curved flanges of the disks.

A rotating cutter 9 having a plurality of radially extending blades 10 is disposed adjacent said contacting curved flange surfaces 5, 6, the cutter blades being adapted to pass during their rotation through a channel formed by two aligned slots 5, 6 to cut the tow which has been fed between the curved flange surfaces. The shaft 11 of the cutter and the shafts 7 and 8 of the disks are linked to a single induction motor via a gear mechanismlnot shown), so that the revolution ratio of the disks to the rotating cutter is constant. Though the revolution speed of the rotating cutter varies in accor dance with conditions, it is about 600 r.p.m. Two detectors 12 and 13 are incorporated to such rotary cutter apparatus; The first detector 12 produces electric pulses equal in number to the number of cutter blades 10 which pass thereover while the rotary cutter 9 rotates, once and the second detector 13 produces a predetermined number of pulses while the rotary cutter 9 rotates once.

FIG. 2 shows the first detector 12 constructed by using a conventional photoelectric switch. A light emitting portion '14 and a light-receiving portion 15 are so arranged as to face to each other, and the cutter 10 is allowed to pass between the two portions 14 and 15. The portion 14 has a light-emitting element in which the light 18 is from a lamp 16 through a lens 17. The emitted light 18 emitted is received by the lightreceiving portion 15 as far as not interrupted by the cutter blade 10. The portion 15 comprises a lens 19, phototransistor 20, amplifier 21, and Schmitt circuit 22. When the light 18 is not interrupted by the cutter blade 10, the collector potential of the phototransistor 20 will be negative so that the output potential of the Schmitt circuit 22 will be zero volts. When the light 18 is interrupted by the cutter blade 10, the collectorpo-.-

tential becomes positive so that the output potential of the Schmitt circuit 22 will be +12 volts.

FIG. 3 shows a circuit of the second detector having a proximity switch. Referring to this circuit, an oscillation coil 24, which works together with ferromagnetic metal pieces 23 (see FIG. I) attached by means of a screw 29 to a blade bed of the rotary cutter 9, is enclosed in a head of the second detector I3. When the metal piece 23 approaches the oscillation coil 24 as shown in the Figure, due to a change in inductance and a change in loss, the oscillator circuit 25 stops its oscillation. As the metal piece 23 retreats from the oscillation. Coil 24, the oscillator circuit 25 restores and maintains its oscillation. Resonance circuit 26, NOT circuit 27, and Schmitt circuit 28 are coupled to the oscillator circuit 25 seriatim, so that when the oscillator circuit 25 is not oscillating, the output potential will be plus 12 volts, and when oscillating, the output potential will be zero volt. i

Accordingly, when the first and second detectors produce pulses, the potential of the output signal from the first or the second detector will be +12 volts. When the output pulses of these detectors distinguish, the potential of the output signal drops from +12 to 0 volt.

For simplification, the output signals from the first and the second detectors hereinafter are referred to as P and P A discriminator to determine breakage of the cutter blades by using pulse signals P and P is illustrated below with reference to several embodiments. In the following illustration, the 0 state and l state stand, respectively, for 0 volt and +12 volts.

In a first embodiment, six ferromagnetic metal pieces 23 are each attached by screw 29 to the blade bed between the space defined by six cutter blades, so that the pulses are produced alternately in time series manner by the first and second detectors. In this embodiment a discriminator shown in FIG. 4a is employed in which a pulse signal P is turned to its opposite pulse signal S through NOTcircuit 102, and is further converted into a positive impulse signal S through a differentialcircuit 103. The impulse signal S is fed to a set terminal of a flip-flop 104, To a reset terminal of the flip-flop 104 are fed a pulse signal P, through OR circuit 107 and an external reset signal. The time at which the flipflop 104 is set and output signal 0, is turned from 0 to l is delayed slightly with respect to the time at which the pulse signal P B is turned from I to O. This delay or lag is caused by the functioning time of the NOT circuit 102, the differential circuit 103, and the flip-flop 104.

The signal Q, and the pulse signal P are fed to AND circuit 105, and output signal S of the AND circuit 105 is fed to a set terminal of flip-flop 106 which receives 7 the external reset signal as a reset signal.

The above-mentioned external reset signal is a pulse which will be produced when either a push button for starting the rotary cutter or a push button for resetting an alarm (not shown) is pushed.

As shown on the left half of FIG. 4b, where there are no broken cutter blades, the flip-flop 104 will have been reset by the pulse signal P, and its output signal Q, will be in 0 state before the pulse signal P is turned from O to I state. On the other hand, as mentioned above, the signal Q, will turn from 0 to 1 immediately after the pulse signal P,, has turned from 1 to 0.

Hence both the output signal S of the AND circuit 105 and the output signal Q of the flip-flop 106 remain in the 0 state. But if one of the cutter blades has been broken, the light will not be interrupted when the broken cutter blade has passed near the photoelectric switch, so that the first detector does not produce the pulse. Pulse Po shown by dotted line on the right of FIG. 4b stands for such not produced pulse. This means that the flip-flop 104 at the time tx is not reset and remains in the set state, and its output Q re-.

mains in the 1 state. By further rotation of the blade b w h f a m systisams t P 3 approaches the second detector 13at the time m, the second detector produces a pulse P whereby the output signal S of the AND circuit 105 is set to the 1 state, and the signal S sets the flip-flop 106 so that its output O is in the 1 state. Thisstate will continue until the above-mentioned external reset signal is received.

The R-S type flip-flop 104 of FIG. 4a is replaceable 5a shows a discriminator which employs the R-S-T type flip-flop. Briefly illustrating, this discriminator resembles the above-mentioned embodiment in that the pulse signal P is converted into an impulse signal S but is different in that the impulse signal S of this circuit triggersthe R-S-T flip-flop 114, which is reset by the pulse signal P,,, and reverses the state. Accordingly, in its op eration, the state of output signal Q of the flip-flop 114 asfar as there is no breakage in the cutter blades is equal to the output signal 0, of the flip-flop 104 shown in the left half of FIG. 4b, and is as shown in the left half of FIG. 5b. But if a cutter blade is broken, and pulse P0 is not produced, the flip-flop 114 will not be reset (the output signal Q remains in the I state). At time tx the pulse signal P B is switched to the 1 state and the output signal 5 of the AND circuit 105 becomes 1, which makes the output signal Q of the flip-flop 106 1. The

flip-flop 114 will be triggered at time 1x by the next received pulse and will be reset.

In the embodiments of FIG. 4a and FIG. 5a the pulse signal P was employed as one of the input signals to the AND circuit 105. But this pulse P may be replaced by a pulse signal P An embodiment of a discriminator using such a pulse signal P is; shown in FIG. 6a. In' the circuit of FIG. 6a, the pulse signal P,, is fed to the AND circuit 105 and, at the same time, is converted into an impulse signal S through NOT circuit 122 and differential circuit 123, which is fed to a set terminal of R-S type flip-flop 128 and to a reset terminal of R-S-T type flip-flop 124 through OR circuit 127. An external reset signal is fed to OR circuit 127 and to the reset terminals of flip-flops 106 and 128. Pulse signal P is fed 5) a trigger terminal of the flip-flop 124. Output signaljQ, of the flop-flop 124 whichwhen reset produces a l-output, is fed to AND circuit 105. Output signal S;, of the AND circuit 105 is fed to a set terminal of flip-flop 106. Out-* put signal O of the flop-flop 128 is fed to the AND circuit 105.

fed to the AND circuit 105, the output signal 8;; of the AND circuit 105 and the output signal Q of the flip-flop 106, respectively, are set to the I state.

The discriminators shown above in FIGS. 40, 5a and 6a can be modified appropriately. For example, the pulse signals P, and P to the flip-flop 104 of FIG. 4a may be fed in opposite relation, and the signal 6 opposite to the output signal 0, of the flip-flop 104 may be fed as the input signal to the AND circuit 105, thereby functioning in substantially the same manner as that shown in the time chart of FIG. 4b. Also, the outputs of OR circuits 107, 127 shown in FIGS. 5a and 6a may be fed to the sq terminals of the flip-flops 114', 124, and the outputs Q and Q of these flip-flops may be fed to the AND circuit 105. Furthermore, the AND circuit 105 shown in FIGS. 4a, 5a and 6a may be replaced by an OR circuit or a NOR circuit. Likewise, AND circuits 135 and 245 shown respectively in FIG. 7a and 8a, which will be described hereinafter, may be replaced by an OR circuit or a NOR circuit. I

In the embodiments mentioned above, the first and the second detectors produced pulses .alternatingly in When the rotary cutter is started,.the discriminator time series manner. g g

In a second embodiment, one ferromagnetic metal piece'23 is attached to the blade bed of the rotary cutter so that the second detector produces one pulse per revolution .of the. rotary cutter. A signal to inform the breakage, of the cutter blade is produced when an even number (or odd number) of output pulse. produced from the first detector, corresponding to the number of cutter blades which should be present during the period of time when the pulses are produced by the second detector is changed into an odd number (or even number). Referring to FIG. 7a, the pulse signal P is fed to a trigger terminal of'R-S-T type flip-flop 134. The pulse signal P from the proximity'switch which is actuated by the single metal piece 23 is fed to AND circuit 135, and at the same time the 'pulse P is converted into an impulse signal S through NOT circuit 132- and differof these pulses has extinguished, the flip-flop 128 'will be set by the first impulse of the impulse signals S Therefore, the output signal Q of the flip-flop 128 will remain in the ls tate until an external reset signal is received. Consequently, the AND circuit 105 will be placed in the condition where it is capable of distinguishing whether the other two inputs P and 0 are simultaneously in the l state. At the same time, the flipflop is reset.

Where there is no breakage of the cutter blades, the pulse signal P, and the signal 0, are not simultaneously in the I state, as shown in the left half of FIG. 6b. Accordingly the output signal S of the AND circuit 105 is the 0 state. However, if a cutter blade is broken, the impulse signal S corresponding to the disappeared pulse Po, i.e., the reset input will not befed tgthe flip} flop 124, and hence pulse signals P as trigger inputs .will successively be fed to the flip-flop 124 at times ential circuit 133, and is fed as aset input to flip-flop 138, and fed as a reset input to the flip-flop 134 through OR circuit 137. An external signal is fed to the OR circuit 137 and to. the reset terminals of the two flipilops 138 and 106. Either one of output signals O or Q of the R-S-T type flip-flop is fed via a switch 139 to the AND circuit l35. TheAND circuit receives an output signal 0 from the flip-flop 138. An output signal S, of the AND circuit 13 is fed to a set terminal of the flip-flop 106.

' The discriminator in this embodiment includes the R-S type flip-flop 138 which has the same function 'asthe flip-flop128 in FIG. 64. Accordingly, after the flip flop'l38 has beenset by the first impulse cuit 135 will be placed in a condition where it is capable of distingui shing whether the pulse signal P,, and the signal Q, (or Q are simultaneously in the 1 state.

The flip-flop 134, on the other hand, is reset by the impulse signal S and is triggered by the pulse signal P,,,

of the impulse S produced by starting the rotary'cutter, the AND cirto the resetterminal of the flip-flop 134 which has been in the reset state, its state will remain unchanged. But the flip-flop 134, after being reset and reversed odd number of times,-will be in a state opposile to the reset state. ,That is, the output signals Q and at this time will, respectively, be 1 and 0. If the impulse signal 8,, is fed to the resetterminal of the flip-flop 134 under this state, flip-flop 134 will necessarily be placed in the reset state. I

Where the number n of cutter blades is an even number, for example, six, the switch 139 should be so set that the output signal Q of the flip-flop 134 is fed to the AND circuit 135. In this case, as shown on the left side of FIG. 7b, if there is no breakage of the cutter blades, the output signal Q of the flip-flop 134 fed to the AND circuit 135 via the switch 139 at the time when the pulse signal P is just turning m1 is already in the 0 state. Hence the output signal S of the AND circuit 135 remains in the 0 state. But if it is assumed that only one cutter blade has been broken, the number of times the flip-flop 134 has reversed will be reduced by one. Accordingly, as shown on the right side of FIG. 71;, when the pulse signal P isjust turning to l, the output signal 0;, of the flip-flop 134 connected to the AND circuit 135 will already be in the l state. Hence the output signal S of the AND circuit 135 will I, which makes the output signal Q flip-flop 106 l.

Where the number n of cutter blades is odd, for example, five blades the switch 139 should be set so that the output signal from the flip-flop 134 is fedto the AND circuit 135. In this case, wherethere is no breakage of the blades, the output signal Q at the time when the pulse signal PE is just turning into I will already be in the 0 state, and the output signal S will remain in the 0 state. But if breakage occurs on the blade, the output signals 0 s; and Q are changed to the I state at the time when the pulse signal P is changing into 1.

Thus, in this embodiment, where the number of the cutter blades is even (or odd), the abnormal signal will be or will not be produced at the time when the pulse signal P is turning into the 1 state depending on whether the flip-flop 134 has been reset (or can be reset) or can be reset (or has been reset).

The discriminator shown in FIG. 8a constitutes a ring counter, in which J-K type flip-flops 144A 144F in number equal to the number of the cutter blades used, for example, six blades are connected like a ring by means of switches 149. This ring counter comprises a flip-flop 142 which is reset by an external reset signal and will be set by the pulse signal P and AND gate 143 which receives as inputs an output signal from the flip-flop 142 and the pulse signal P and feeds its (AND gate 143) output as trigger inputs to the flip-flops 144A 144F constituting the above-mentioned ring counter. If the R-S flip-flop 142 is reset by the external reset signal before the pulse signal P is produced, i.e., when the cutting device is being started (fi h); the AND gate 143 will be closed. Simultaneously, the external reset signal causes the flip-flop 144A to be preset so that its output signal 0,, becomes the l, and causes other flip-flops 144B 4 144F to be cleared so that their counter, the first pulse p of said pulse signals P will set the output signal Q of the .l-K flip-flop 144A to the 0 state, and will set the output signal Q of the next flipflop 1448 to the I state. The second pulse p then sets the output signal Q to the 0 state and the output signal O of the following flip-flop 144C to the I state. In this way, the third, fourth and fifth pulses p P and P successively set the output signals O O and Q the l state. The sixth pulse P then sets the output signal 0,- to the 0 state and the output signal Q to the 1 state. When there is no breakage of the cutter blades, six pulses will pass through the AND gate 143 during each period between successive pulse signalsP The abovementioned operation will be repeated,- and every one of respective output signals Q -O,- become 0. Then if the pulse signal P for the first time becomes l at time t the flip-flop 142 will be reset, and the AND gate 143 will be opened. As a result, the pulse signal P passed through the AND gate 143 triggers every J-K flip-flop 144A 144F. Since J-K flip-flops 144A 144F the ring the J-K flip-flops 144A 144F will function as shown in the time intervel Tx of FIG. 8b. In this way, where the pulse signal P is in the I state, the outpugignal Q, will be in the I state and its opposite signal Q4 Will be in the 0 state.

The discriminator has an AND ciguit 145 which receives as inputs the output signal Q4 of the flip-flop 144A and the pulse signal P Qutput signal S of the AND circuit 145 sets the flip-flop 106, and the flip-flop 106 is reset by the external reset signal. When there is no breakage of the cutter blades, and where the pulse signal P is in the 1 state, the output signal 6 will be in the 0 state as mentioned above. Hence the output signal 8,, of the AND circuit 145 will always be in the 0 state.- But if one of the cutter blades breaks, as shown in the time interval Ty of FIG. 85, only five pulses will pass through the AND gate 143 during one cycle (or period) of the pulse signal P,,. Accordingly, the time required for the output signal 0,; to turn itself into the I state will double compared to the normal instance, and

the change of the output signals Q Q1), Q6, and Q will be delayed a little compared to their normal response. Therefore, when the pulse signal P is just turning into the 1 state, the output signal Q will be in the I state, and the output signal Q,, will be still in the 0 state (output signal Q, is in the 1 state). Hence the output signal S,, of the AND circuit 145 will be switched to the 1 state, and the output signal 0 of the R-S fiip-flop will be set to the 1 state. 4

' Although the time interval following the interval Ty has not'been shown in FIG. 8b, when the pulse signal P is just becoming l, the output signal 0;; in this interval (following the interval Ty) will be in the 1 state. Furthermore, in the next interval, when the pulse signal P is just becoming l the output signal Q], will be in the 1 state. Accordingly, in place of the output signal 6 any one of the output signals Q Q Q Q or-Q may be put into the AND circuit 145. Also, instead of putting the signal (1, into the AND circuit 145, the output signals Qn, Qr, Q1, Q and Or may be'put into one OR circuit, and the output signal of the OR circuit may be put into'the AND circuit 145.

In this embodiment, when the number of the cutting blades isto be changed, for example, from six to five blades, one needs only to advance the switch 149 for one step in the clockwise direction.

A final embodiment employing a discriminator shown in FIG. 9a shall be described hereinafter. In this embodiment, a pulse is produced from the-first detector as each cutter blade passes a predetermined point. However, this embodiment is different from the abovementioned first and second embodiments in that the second detector produces one pulse for every m (an integer of 2 or more) rotations of the cutter blades. In the embodiment shown in the Figure, a frequency divider 151 which divides frequency into l/m is provided on the output side of a proximity switch which is actuated by a single metal piece 23, so that when m 32 4, every time when the frequency divider 151 received four pulses from the approach switch, the frequency divider 151 triggers a monostable multivibrator 152 once, thereby causing the monostable multivibrator 152 to produce a pulse several milliseconds in width. The output signal from this monostable multivibrator 152 shall be hereinafter referred to as pulse signal P Of course an auxiliary shaft driven by the cutter shaft through a reduction gear having a reduction ratio of l/m may be used in place of the frequency divider 151 to produce a single pulse P,, for every rotation of the auxiliary shaft. This discriminator has a binary counter comprising five flip-flops 156A 156E to count the pulse signals P, fed through AND gate 157. The value of the counter will return to zero if the counter is cleared by signal 8,, which is converted from said pulse signal P,, through NOT circuit 153 and differential circuit 154. The pulse signal P can pass the AND gate 157 after an R-S type flip-flop 155 reset at time to by an external reset signal, is set by the first impulse signal S at time 1,.

A setting means 158 composed of anND circuit receives every output signalsO Q On Q, and 0,; from flip-flops 156A 156E forming a counter, and the output pulse 510 thereof becomes the I state when these output signals are all in the l state.

R-S fip-flop 159 is set by the impulse signal 8,, produced when the pulse signal P,;- turns from I state to 0 state and is reset by the signal S,,,. Output signal Q from the flip-flop 159 is fed to AND circuit 160 together with the pulse signal P This flip-flop 159 and the AND circuit 160 form a gate circuit 161 to determine whether the pulse signal P is permitted to pass through toward a flip-flop 106. It will easily be understoodthat the gate circuit 161 is opened by the impulse signal S,, and closed by the signal If none of the six cutter blades break, the counter 156 will count 6 X 4, i.e., 24 pulses while the rotary cutter rotates four times. Hence, after the pulse is produced from the monostable multivibrator 152, the counter 156 will count 22 pulses before the rotary cutter rotates four times thereby establishing a relation O =Q =Q =O =Q =L Accordingly, the output signal Sm of the setting means 158 is l, which closes the gate circuit 161. Hence if the rotary cutter has rotated four times, and a pulse is produced again from the monostable multivibrator 152, said pulse cannot pass through the gate circuit 161.

But ifit is assumed that one of six cutter blades is broken, the counter will count only (6 l) X 4, i.e., 20 pulses P while the rotary cutter rotates four times. Hence when the rotary cutter has rotated four times after the pulse has been produced from the monostable multivibrator-J52, the counter cannot hold a relation Q ,=Q,,=Q =Q,,=Q =l. Hence the gate circuit 161 will be left open. And when the rotary cutter has rotated four times and the monostable multivibrator 152 has produced a pulse, said pulse will pass through the gate circuit 161, setting the flip-flop 106, so that the output signal O2 is set to l. 1

If the number of the cutter blades employed is n, a

setpoint a of the setting means 158 will most desirably 10 be (n /2)m which is a central value between n m and (n l)m. But if m is an odd number, the setpoint a may be (n /2)m V2 or (n V2)": V2. But where m is greater than 4, the setpoint a need not be set strictly tothe central value, but may be set near the central value. Also, where the number of the cutter blades is changed, the setpoint amay be increased or decreased by a multiple of m. If illustrated with m 4, the switch can be operated easily to select signals as shown in the table below so as to give inputs to the setting means 158.

The discriminator according to this embodiment has such an advantage that, even when the fiber scattered from the tow having been cut passes through the photoelectric switch of the first detector 12 to cause additional pulses to be superposed onto the pulse signal P or even where more electric noise is present in the first detector compared to the second detector, no abnormal signal Q will be developed, provided the number of superposed pulse or noise is smaller than a i (n The final output signal Q producedby the discriminator mentioned above in all cases remains in the 0 state so long as the cutter blade 9 remain unbroken, and is set to 1 when; the breakage occurs on the cutter blades 9. It will be relatively easy to actuate an alarm or to automatically stop the rotary cutter by means of the output signal Q2 which is in the 1 state. FIG. 10 shows such acircuit.

Referring to FIG. 10, where the output signal O is in the 0 state, i.e., zero volts, transistors 160, 161 will be in the cut of T state and relay 162 is not excited. But if the output signal O is in the 1 state, i.e., +l2 volts,

the both transistors 160, 161 will be made conductive, 'so that the relay 162 is excited, and the contact point output will be rendered conductive. The contact point output actuates thealarm bell (not shown) or cuts off the power switch connected to the motor driving the rotary cutter. v

In the foregoing are illustrated embodiments of this invention, but the detecting means of the first detector 12 shall not be limited to the photoelectric switch.

Since the material of the cutter blades 10 are usually made of a magnetic metal, a proximity switch which is magnetically actuated may be employed. FIG. 11 shows an embodiment in which the proximity switch 30 is employed as the detecting means of the first detector 12. However, if the proximity switch 12 is adapted to a bias cut in which the cutter blades are alternatingly attached at different angles, for example 20, with respect to vertical planes, two such approach switches will be required. That is, one is for detecting half the number of the blades in one direction, and the other is for detecting the remaining blades in the other direction. In contrast, only one photoelectric switch will be sufficient even for'the bias cut.

The detecting means of the second detector 13 shall not be limited to the proximity switch either and may be replaced by a photoelectric switch. In the embodiment shown in FIG, 11, a detecting means of the second detector 13' comprises a band 32 secured to the shaft 11 of the rotary cutter or another shaft operatively connected to the rotary shaft and a rod 31 radially extending from the band. The rod 31 isrotatedand interrupts the light between the opposing light-emitting portion 33 and light-receiving portion 34 of the second detector 13. Preferably, the photoelectric switch is mounted to be free from the scattered fiber from the tow having been cut, for example, at a place adjacent the lower portion of the rotary shaft 11.

What is claimed is:

1. An apparatus for detecting broken blades in a rotary cutter for a tow having at least two radially disposed cutter blades, comprising:

a first detecting member operatively positioned relative to said rotary cutter for producing a pulse each time a cutter blade passes a predetermined location;

a second detecting member operatively positioned relative to said rotary cutter for producing at least one pulse, the exact number thereof being predetermined, for every predetermined number of revolutions of said rotary cutter, said pulses from said second detecting member defining a time period during which the number of puises produced by said first detector normally reaches the predetermined number; I

and a discriminator member connected to said first and second detector members and producing an abnormal indication signal when the number of pulses produced by said first'detector in said time period is less than the predetermined number. 2. An apparatus as claimed in claim 1, wherein said first detector comprises a photoelectric switch having a light-emitting element and an opposing lightreceiving element, said elements allowing the tips of v the cutter blades to -pass through. p

3. An apparatus as claimed in claim 1, wherein-said first detector comprises a proximity switch which ismagnetically actuated when-the tip of said cutter blade approach thereto. I a I 4. An apparatus as claimed in claim l, wherein said second detector comprises a ferromagnetic metal'piece which rotates with the rotation of said, rotary cutter, and a proximity switch which is magnetically actuated when said metal piece approaches thereto. 5. An apparatus as claimed in claim 1 wherein sai second detector comprises a photoelectric switch having a light-emitting element and an opposing lightreceiving element, and a light shielding member rotating with the rotation of said rotary cutter. and passing between both elements tointermittently interrupt the light received by said light emitting element. 6. An apparatus for detecting breakage of at leastone of the blades of a rotary butter for a tow in which N cutter blades are radially disposed, N being greater than 1,

comprising: I a

a first detector which produces, a pulse for every pass of a tip of the cutter blade position: I

acrossa predetermined a second detector which produces n pulses forevery revolution of said rotary cutter, the time interval between successive ones of said It pulses per revolution being a period of time during which one pulse is normally produced by said first detector; and i a discriminator receiving the output pulses from the first and second detectors to produce an abnormal v indication signal when no pulse is received from said first detector during said period of time between successive pulses produced bysaid second detector.

' 7. An apparatus as claimed in claim 6 wherein said discriminator comprises:

a fiip flop which receives, as a set input, the output pulse from said second detector and receives, as a reset input, the output pulse from said first detector, and

an AND circuit which receives, as inputs, an output rectangular wave from said flip-flop and the output pulse from said second detector, said AND circuit producing a pulse signal only when said flip-flop has already been in a set state but at the time when the output pulse is received from said second detector, said abnormal indication signal being the output pulse of said AND circuit.

8. An apparatus as claimed in claim 6 wherein said discriminator comprises:

a flip-flop which receives, as a trigger input, the outi in a statecontrary to a reset state but at the time when the output pulse is received from said second detector, said abnormal signal being the output pulse of said AND circuit.

9. An apparatus as claimed in claim discriminator comprises:

a flip-flop which receives, as a trigger input, the output pulse from said second detector and receives,

as a reset input, the output pulse from said first detector, and I an AND circuitwhich receives, as inputs, an output 6, wherein said rectangular wave from said flip-flop and the output pulse from said first detector, said AND circuit producing a pulse signal only when said flipflop has already been in a reset state but at the time when the output pulse is received from said first detector, said abnormal indication signal being the output pulse of said AND circuit.

10. An apparatus for detecting breakage of at least one of blades of a rotary'cutter for a tow in which n( an a integer of 2 or more) cutter blades are radally disposed,

comprising:

a first detector which produces a pulse for every pass of'a tip of the cutter blade acrossapredetermined position,

a second detector which produces one pulse for every rotation of said rotarycutter, said pulses being produced to have a period of time during which n units of pulses are normally produced by said first detector, and

a discriminator receiving the output'pulses from said first and second detectors to produce an abnormal indication signal when the number of pulses produced by the first detector during said period of time of said pulses produced by said second detector is smaller than n.

11. An apparatus as claimed in claim 10, wherein said discriminator comprises: v

a flip-flop which receives the output pulses from said first and said second detectors, respectively, as a trigger input and reset input, and

and AND circuit which receives as inputs an output rectangular wave from said flip-flop and the output pulse of said second detector, wherein said AND circuit upon receipt of the pulse from said second detector produces a pulse with said flip-flop either in a state opposite to a reset state or in a reset state, depending on whether n is an even or odd number, said abnormal indication signal being the output pulse of said AND circuit.

12. An apparatus as claimed inclaim 10, wherein said discriminator comprises:

a ring counter having n units of flip-flopsconnected in a ring form, wherein a determined flip-flop is preset to 1 before said second detector produces a first pulse and the other flip-flops are cleared to 0,

said discriminator comprises:

said ring counter being triggeredby the output pulse of said first detector after said second detector has produced the first pulse, and an AND circuit which receives, as inputs, an output rectangular wave contrary to the output of saidflip-flop and the output pulse from said second detector, said abnormal indication signal being the output pulse of said AND circuit. 13. An apparatus for detecting breakage of at least one of blades of a rotary cutter for a tow in which n(an 14 integer of 2 or more) cutter blades are radially disposed, comprising: v

a first detector-which produces a pulse for every pass of a tip of the cutter blade across a position, v

a second detector which produces one pulse for m(an integer of 2 or more) times of the number of revolutions of said rotary cutter,said pulse being produced to have a period of time during which nm units of pulses are normally produced by said first detector, and

a discriminator receiving the output pulses from said first and second detectors to produce an abnormal indication signal when the number of pulses produced by the first detector during the period of time of said pulses produced by said second detect tor is smaller than reference value determined near the center between nm and (n 1)m.

14. An apparatus as claimed in claim 13, wherein second detector passing through said gate circuit.

predetermined 

1. An apparatus for detecting broken blades in a rotary cutter for a tow having at least two radially disposed cutter blades, comprising: a first detecting member operatively positioned relative to said rotary cutter for producing a pulse each time a cutter blade passes a predetermined location; a second detecting member operatively positioned relative to said rotary cutter for producing at least one pulse, the exact number thereof being predetermined, for every predetermined number of revolutions of said rotary cutter, said pulses from said second detecting member defining a time period during which the number of pulses produced by said first detector normally reaches the predetermined number; and a discriminator member connected to said first and second detector members and producing an abnormal indication signal when the number of pulses produced by said first detector in said time period is less than the predetermined number.
 2. An apparatus as claimed in claim 1, wherein said first detector comprises a photoelectric switch having a light-emitting element and an opposing light-receiving element, said elements allowing the tips of the cutter blades to pass through.
 3. An apparatus as claimed in claim 1, wherein said first detector comprises a proximity switch which is magnetically actuated when the tip of said cutter blade approach thereto.
 4. An apparatus as claimed in claim 1, wherein said second detector comprises a ferromagnetic metal piece which rotates with the rotation of said rotary cutter, and a proximity switch which is magnetically actuated when said metal piece approaches thereto.
 5. An apparatus as claimed in claim 1 wherein said second detector comprises a photoelectric switch having a light-emitting element and an opposing light-receiving element, and a light shielding member rotating with the rotation of said rotary cutter and passing between both elements to intermittently interrupt the light received by said light emitting element.
 6. An apparatus for detecting breakage of at least one of the blades of a rotary cutter for a tow in which N cutter blades are radially disposed, N being greater than 1, comprising: a first detector which produces a pulse for every pass of a tip of the cutter blade across a predetermined position: a second detector which produces n pulses for every revolution of said rotary cutter, the time interval between successive ones of said n pulses per revolution being a period of time during which one pulse is normally produced by said first detector; and a discriminator receiving the output pulses from the first and second detectors to produce an abnormal indication signal when no pulse is received from said first detector during said period of time between successive pulses produced by said second detector.
 7. An apparatus as claimed in claim 6 wherein said discriminator comprises: a flip-flop which receives, as a set input, the output pulse from said second detector and receives, as a reset input, the output pulse from said first detector, and an AND circuit which receives, as inputs, an output rectangular wave from said flip-flop and the output pulse from said second detector, said AND circuit producing a pulse signal only when said flip-flop has already been in a set state but at the time when the output pulse is received from said second detector, said abnormal indication signal being the output pulse of said AND circuit.
 8. An apparatus as claimed in claim 6 wherein said discriminator comprises: a flip-flop which receives, as a trigger input, the output pulse from said second detector, and receives, as a reset input, the output pulse from said first detector, and an AND circuit which receives, as inputs, an output rectangular wave from said flip-flop and the output pulse from said second detector, said AND circuit producing a pulse signal only when said flip-flop is in a state contrary to a reset state but at the time when the output pulse is received from said second detector, said abnormal signal being the output pulse of said AND circuit.
 9. An apparatus as claimed in claim 6, wherein said discriminator comprises: a flip-flop which receives, as a trigger input, the output pulse from said second detector and receives, as a reset input, the output pulse from said first detector, and an AND circuit which receives, as inputs, an output rectangular wave from said flip-flop and the output pulse from said first detector, said AND circuit producing a pulse signal only when said flip-flop has already been in a reset state but at the time when the output pulse is received from said first detector, said abnormal indication signal being the output pulse of said AND circuit.
 10. An apparatus for detecting breakage of at least one of blades of a rotary cutter for a tow in which n(an integer of 2 or more) cutter blades are radally disposed, comprising: a first detector which produces a pulse for every pass of a tip of the cutter blade across a predetermined position, a second detector which produces one pulse for every rotation of said rotary cutter, said pulses being produced to have a period of time during which n units of pulses are normally produced by said first detector, and a discriminator receiving the output pulses from said first and second detectors to produce an abnormal indication signal when the number of pulses produced by the first detector during said period of time of said pulses produced by said second detector is smaller than n.
 11. An apparatus as claimed in claim 10, wherein said discriminator comprises: a flip-flop which receives the output pulses from said first and said second detectors, respectively, as a trigger input and reset input, and and AND circuit which receives as inputs an output rectangular wave from said flip-flop and the output pulse of said second detector, wherein said AND circuit upon receipt of the pulse from said second detector produces a pulse with said flip-flop either in a state opposite to a reset state or in a reset state, depending on whether n is an even or odd number, said abnormal indication signal being the output pulse of said AND circuit.
 12. An apparatus as claimed in claim 10, wherein said discriminator comprises: a ring counter having n units of flip-flops connected in a ring form, wherein a determined flip-flop is preset to 1 before said second detector produces a first pulse and the other flip-flops are cleared to 0, said ring counter being triggered by the output pulse of said first detector after said second detector has produced the first pulse, and an AND circuit which receives, as inputs, an output rectangular wave contrary to the output of said flip-flop and the output pulse from said second detector, said abnormal indication signal being the output pulse of said AND circuit.
 13. An apparatus for detecting breakage of at least one of blades of a rotary cutter for a tow in which n(an integer of 2 or more) cutter blades are radially disposed, comprising: a first detector which produces a pulse for every pass of a tip of the cutter blade across a predetermined position, a second detector which produces one pulse for m(an integer of 2 or more) times of the number of revolutions of said rotary cutter, said pulse being produced to have a period of time during which nm units of pulses are normally produced by said first detector, and a discriminator receiving the output pulses from said first and second detectors to produce an abnormal indication signal when the number of pulses produced by the first detector during the period of time of said pulses produced by said second detEctor is smaller than reference value determined near the center between nm and (n - 1)m.
 14. An apparatus as claimed in claim 13, wherein said discriminator comprises: a counter which is cleared to 0 by the pulse signal from said second detector and counts the pulse signals produced by said first detector, and a gate circuit which is closed when the counted value of said counter reached said reference value, and is opened when the pulse signal from said second detector has extinguished, and receives, as an input, the pulse from said second detector, said abnormal indication signal being the pulse from said second detector passing through said gate circuit. 